1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a wireless network system and a method of transmitting or receiving data over a wireless network, and more particularly, to a wireless network system and a method capable of limiting the transmission or reception of request packets by stations existing on the wireless network, where directional communication is performed in a high-frequency bandwidth, while a wireless network coordinator is being changed or while the wireless network coordinator is in a busy state.
2. Description of the Related Art
FIG. 1 illustrates a conventional superframe 100. The conventional superframe 100 sequentially includes a beacon period 110, a contention access period (CAP) 120, and a channel time allocation period (CTAP) 130. During the CAP 120, asynchronous data or control commands are transmitted or received. The CTAP 130 is composed of channel time allocations (CTA's) 132 and management CTA's (MCTA's) 131. The CTA's 132 are used to transmit or receive control commands, isochronous data, and asynchronous data.
The length of the CAP 120 is determined by an access point (AP) and is communicated to stations, which exist on a network, using a beacon frame broadcast during the beacon period 110.
The CAP 120 uses a carrier sense multiple access with collision avoidance (CSMA/CA) method as a media access method. On the other hand, the CTAP 130 uses a time division multiple access (TDMA) method in which each station has a specified time window. The AP allocates a channel time for a device requesting media access and exchanges data with a corresponding station during the allocated channel time. Here, the MCTA's 131 are either allocated to a pair of stations, which desire to exchange data with each other and use the TDMA method for access, or they are shared CTA's using a slotted aloha protocol.
Presently, a method of transmitting compressed data using a bandwidth of several gigahertz and a method of transmitting uncompressed data using a frequency bandwidth of several tens of gigahertz are being developed. However, since uncompressed data is larger than compressed data, it can be transmitted only in a frequency bandwidth of several tens of gigahertz. In addition, even when having packet loss, uncompressed audiovisual data is less affected by the packet loss than the compressed data in terms of display quality.
Therefore, in order to transmit or receive data in such a high frequency bandwidth, each station may transmit a request packet to a coordinator requesting the coordinator to allocate a frequency bandwidth and approve its participation in a network. However, if a station transmits a request packet to the coordinator while network management authority is being handed over from a network coordinator to a new network coordinator, a new coordinator may fail to receive the request packet. Similarly, a coordinator in a busy state may be unable to service the request packet and may fail to receive the request packet. Accordingly, the station which transmitted the request packet cannot receive a response packet from the new coordinator, or the busy coordinator, and has to retransmit the request packet, thereby causing a loss of a communication bandwidth.
In this regard, an invention is required that can prevent a loss of a communication frequency bandwidth by limiting the transmission or reception of request packets by stations while network management authority is being handed over from a network coordinator to a new network coordinator or while a network coordinator is in a busy state.